Knee Synovitis

Knee synovitis

Knee synovitis occurs when the synovial membrane which lines and lubricates the knee joint, becomes inflamed. Swelling or stiffness are symptoms that may follow another injury, arthritis, or gout.


Medically reviewed by Dr Chaminda Goonetilleke, 21st Dec. 2021

Symptoms of knee synovitis

Symptoms include:

  • Pain, swelling, and stiffness in the knee joint.
  • The knee may feel warm and inflamed.
  • It may appear red over the painful area.

Further investigations include taking a sample of fluid from the joint with a needle and considering further imaging to explore possible causes. In cases of arthritis, infection, or gout – an MRI is unnecessary.

What is Knee synovitis?

Knee synovitis occurs when the synovial membrane which lines and lubricates the knee joint, becomes inflamed. Synovitis may be caused by other conditions, such as rheumatoid arthritis or gout. Or it may simply develop on its own.

knee synovitis

All of the large joints in the body (such as the knee, hip, and shoulder) are synovial joints. These joints are surrounded by a synovial membrane that encapsulates the joint. Its purpose is to lubricate it by secreting synovial fluid.

This lining can become inflamed, causing pain and stiffness in the joint.

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What causes synovitis?

Synovitis is usually a secondary condition. This means it is caused by another ailment or injury. Possible causes include:

  • Arthritis – this is wear and tear in the joint
  • Knee injuries
  • Infection in the joint
  • Gout – this is a painful condition affecting joints.
  • Cancer – it is important that if you have synovitis then it is investigated properly.

Treatment for knee synovitis

Treatment depends on what is causing your synovitis.

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Cold therapy

If you have or had a knee injury, then apply the PRICE principles of protection, rest, ice, compression, and elevation.


If you have arthritis, then anti-inflammatory medications are usually successful.


In cases caused by more serious conditions or injuries then treating the underlying cause is most important. However, your surgeon may use arthroscopic surgery to remove the affected synovial tissue.

Pigmented villonodular synovitis (PVNS)

This form of synovitis is rare but more serious. It results in an overgrowth of the synovial membrane itself. As a result, a benign tumour develops. The knee and hip joints are most frequently affected.

Symptoms of PVNS include episodes of pain and swelling which comes and goes. Pain gradually gets worse over time. Your knee joint sometimes catches or locks.

If you do not catch PVNS early, it may spread to other tissues. Your doctor will order an MRI scan and drain synovial fluid from your knee for testing. They may also do a biopsy to confirm the diagnosis.

Treatment usually involves removing the tumour, via a synovectomy. In other words, removing the affected lining. However, approximately 45% of cases reoccur. Therefore, radiation therapy may also be used. In severe cases which continue to recur, your doctor may advise you to have a full knee replacement operation.

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